Pressure-tuning of the c-f hybridization in Yb metal detected by infrared spectroscopy up to 18 GPa

TL;DR

This study uses infrared spectroscopy to investigate how pressure affects the electronic hybridization in ytterbium metal, revealing a decrease in hybridization strength up to 18 GPa, which correlates with valence changes.

Contribution

It provides the first infrared spectroscopic evidence of pressure-induced changes in c-f hybridization in elemental Yb up to 18 GPa.

Findings

Infrared reflectivity shows a pressure-dependent deep minimum in mid-infrared.

The minimum shifts to lower energy as pressure increases.

Results indicate decreasing c-f hybridization with increasing pressure.

Abstract

It has been known that the elemental Yb, a divalent metal at mbient pressure, becomes a mixed-valent metal under external pressure, with its valence reaching ~2.6 at 30 GPa. In this work, infrared spectroscopy has been used to probe the evolution of microscopic electronic states associated with the valence crossover in Yb at external pressures up to 18 GPa. The measured infrared reflectivity spectrum R(w) of Yb has shown large variations with pressure. In particular, R(w) develops a deep minimum in the mid-infrared, which shifts to lower energy with increasing pressure. The dip is attributed to optical absorption due to a conduction c-f electron hybridization state, similarly to those previously observed for heavy fermion compounds. The red shift of the dip indicates that the $c$-$f$ hybridization decreases with pressure, which is consistent with the increase of valence.